This section introduces aspects that may help facilitate a better understanding of the invention. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is prior art or what is not prior art.
A differential current circuit is a circuit that simultaneously generates a pair of currents: an outgoing source current and an incoming sink current. The goal of a differential current circuit is to generate precisely matched source and sink currents that have identical magnitudes.
FIG. 1 shows a schematic circuit diagram of conventional differential current circuit 100, which generates source current Isource and sink current Isink In circuit 100, PMOS devices Pm, Ps1, and Ps2 are configured as current mirrors, where the current Iin through master device Pm is mirrored by the currents through both the first slave device Ps1 and the second slave device Ps2 and where the mirrored current through device Ps2 is the source current Isource for circuit 100. The mirrored current through the first slave device Ps1 passes through the first NMOS tail device Nt1. With their gates interconnected and their sources both connected to ground, the current through the first tail device Nt1 is mirrored by the current through the second NMOS tail device Nt2, which is the sink current Isink for circuit 100.
Under ideal conditions, the source current Isource and the sink current Isink generated by differential current circuit 100 would have identical magnitudes. However, in the real-world implementations, processing mismatches and drain voltage differences between the PMOS devices, Ps2 and Ps1, and, similarly, between the NMOS devices, Nt2 and Nt1, lead to a mismatch between the magnitudes of those source and sink currents.